• Grabulosa, Adrià
• Moughames, Johnny
• Porte, Xavier
• Brunner, Daniel

Abstract

Low-loss single-mode optical coupling is a fundamental tool for most photonic networks, in both, classical and quantum settings. Adiabatic coupling can achieve highly efficient and broadband single-mode coupling using tapered waveguides and it is a widespread design in current 2D photonic integrated circuits technology. Optical power transfer between a tapered input and the inversely tapered output waveguides is achieved through evanescent coupling, and the optical mode leaks adiabatically from the input core through the cladding into<br&gtthe output waveguides cores. We have recently shown that for advantageous scaling of photonic networks, unlocking the third dimension for integration is essential. Two-photon polymerization (TPP) is a promising tool allowing dynamic and precise 3D-printing of submicrometric optical components. Here, we leverage rapid fabrication by constructing the entire 3D photonic chip combining one (OPP) and TPP with the (3+1)D flash-TPP lithography configuration, saving up to ≈ 90 % of the printing time compared to full TPP-fabrication. This additional photo-polymerization step provides auxiliary matrix stability for complex structures and sufficient refractive index contrast Δn ≈ 5×10−3 between core-cladding waveguides and propagation losses of 1.3 dB/mm for single-mode propagation. Overall, we confront different tapering strategies and reduce total losses below ∼ 0.2 dB by tailoring coupling and waveguides geometry. Furthermore, we demonstrate adiabatic broadband<br&gtfunctionality from 520 nm to 980 nm and adiabatic couplers with one input and up to 4 outputs. The scalability of output ports here addressed can only be achieved by using the three-spatial dimensions, being such adiabatic implementation impossible in 2D.

Topics

• impedance spectroscopy
• lithography